Process of coloring metal



Nov. 22, 1938. F. A. TUERFF I PROCESS OF COLORING METAL Original Filed March 30, 1934 INVENTOIR rilzur- Then) Frank A WP J ORNEY Patented Nov. 22, 1938 PROCESS OF COLORING METAL Frank Arthur Tuerff, Newark, N. J., assignor to Windsor Mfg. 00., Orange, N. 1., a corporatio of New Jersey Application March 30, 1934, Serial No. 718,117

Renewed September 7, 1937 11 Claims.

This invention relates to processes of treating metal. It is particularly directed to a method of treating steel to impart to the surface thereof a blue finish.

An object of this invention is to provide a highly improved method of the character described, for blueing the surface of steel, for example, strip steel for razor blades, without softening the steel, whereby hardness, as is required. for example, in razor blades, may be obtained, independently of the color. Heretofore, steel had been blued by tempering, but the tempering process softened the steel. With my improved method, the hardness requisite in certain articles,

for example, razor blades, is retained, and the blue color'nevertheless obtained.

A further object of this invention is to provide an improved and simple process of the character described, which shall be economical to carry out, and which shall nevertheless be practical and eflicient to a high degree.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

The invention accordingly consists in the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter described, and of which the scope of application will be indicated in the following claims.

In the accompanying drawing, in which is shown one of the various possible illustrative embodiments of this invention,

Fig. 1 is a top plan view, partly diagrammatic, and partly in cross-section, of the apparatus for carrying out my improved method;

Fig.2 is an enlarged, cross-sectional view taken on line 2--2 of Fig. 1; i

Fig. 3 is a vertical, transverse, cross-sectional view of the furnace;

Fig. 4 is a cross-sectional view taken on line 4-4 of Fig. 2; and

Fig. 5 is a cross-sectional view taken on line 55 of Fig. 2.

The drawing represents a satisfactory form of apparatus for carrying out myimproved method, it being understood, however, that my invention is not restricted to the specific form of the apparatus illustrated in the drawing. 1

" ,'In the drawing II'I designates a furnace form'- ing part of the equipment for imparting a blue oxidized surface to a strip of steel I I, here, shown for the purpose of illustration as an elongated;

thin strip of steel stamped to form razor blades.

spaced from the walls thereof.

for the razor blades. The furnace I0 may comprise a cylindrical member Iland may be made of any suitable heat resistant material. The same is formed with a plurality of spaced. openings I6" at the top.

Extending through the furnace, substantially axially thereof is an elongated, horizontal, flattened tube I8 of a heat resistant alloy, for example, nichrome. The tube I8 is open at the opposite ends thereof; At one end I9 the tube projects beyond the cylindricalmember I4 which is closed by a plate 20, at said end, formed with an opening to permit the tube I8 to pass therethrough. For supporting the tube I8, a plurality of horizontal, spaced bars 22 are fixed at the op- 'posite ends thereof within the cylindrical member I4 contacting the underside of the tube. opposite end vof the cylindrical member I4 is closed by a plate 25 of heat resistant material, for example, asbestos. The plate 25 is cut out on the inner face thereof to receive-the end 26 of the tube I8. The upper half of the tube is substantially entirely closed by the plate 25, and by an additional sheet 28 of asbestos placed on the outer surface of the plate 25. The cut out opening in the plate 25 is preferably somewhat greater at the bottom than the transverse outline of the tube I8, as shown in Fig. 4 of the drawing.

A small steel strip 30 is interposed within said space to insure spaces 3| and 32 on opposite sides thereof. A sheet 34 of asbestos is also placed against the outer surface of the plate 25 in alignment with the lower half of the tube, but said plate 34 is spaced from the end 26 of the nichrome tube, thus permitting communication between the inside of the furnace and the interior of the tube I8 at the end 28 of the latter.

The steel strip II is fed continuously through the nichrome tube I8 and is so guided as to be The steel strip II passes between the asbestos sheets 28 and 34 which form a very narrow slot to permit passage of the steel strip.

It will thus be noted that the furnace is entirely closed to the outside except through the openings I6 at the top, and communication between the interior of the tube l8 and the interior of the furnace may only be had through the spaces 3| and 32. An additional narrow slot 40 may be formed in the upper portion of the tube I8 and somewhat adjacent the end 26 thereof, although I have foundthat the blueing process maybe carried out without said slot.

The furnace may be heated with a gaseous fuel consisting of a mixture of air and carbon mon- 'The oxide. The air may be supplied by a pipe 4| extending preferably to the outside atmosphere as at 42, to ensure a constant and ample supply of air. The air through the pipe 4| is fed under 5 pressure by a motor operated compressor blower 43 to a pipe 44 which may be provided with a gate valve 45. The pipe 44 communicates with the pipe 48 which may be divided into three branch pipes 41, 48 and 49, each preferably having a hand operated gate valve. Ordinary illuminating gas or carbon monoxide may be supplied through a pipe 50 communicating with the pipe 5|, likewise having three branches 52, 53 and 54. The branches 4! and 52 join to form a pipe 56. The branches 48 and 53 join to form a pipe 51 and the branches 49 and 54 join to form a pipe 58. Extending from each of the pipes 55, 51 and 58 into the furnace from opposite sides thereof, are a plurality of branch pipes or jets 60 which are lit to heat the furnace. The pipes 52, 53 and 54 may likewise be provided with the usual hand operated valves. The flow of air and carbon monoxide may be simultaneously increased or decreased by any suitable control member 65, preferably-electrically operated, and controlled by a thermostat 66. A regulator 61 connected to the thermostat 66 and the control member 65, may serve to maintain the temperature within the furnace at any temperature to which the regulator may be set. The proportion of the fuel mixture may be regulated by valves 10 and 1| in the pipes 44 and 50 operated by pointers or handles 12 and 13 overlying a scale 14. Thus, if it is desired to increase the amount of air, the pointer or handle 12 may be rotated, and for changing the amount of C0 gas the pointer 13 may be rotated. The scale 14 will indicate the relative proportions of the fuel constituents. I have found that by merely regulating the valve in the pipe 52, the proportion of air in the furnace is increased and the color of the strip is changed without effecting the temperature adjacent the outlet side of the furnace. The hardness of the steel strip is thus unchanged as the color is changed.

Extending into the receiving end IQ of the tube I8 is a pipe 80' to which is fed ordinary illu- 'minating gas. This gas is burned substantially at the mouth of the tube l8 so that the flame may escape through said mouth. The flange on the tube 30 serves to burn oil and other products from the surface of the steel strip II.

The air in the fuel is an oxidizing agent, whereas the CO is a reducing agent. I The furnace is heated to a temperature between 30 and 1600 F. which is above the critical temperature of the steel. pipes 41, 48 and 49 and the pipes 52, 53 and 54 are so regulated that the furnace becomes hotter gradually from the left to the right, looking at Fig. 1. The steel strip is thus heated progressively to a temperature above its critical point and I have found that the surface thereof becomes oxidized and blued as it passes through the furnace, the excess of unburned o'xygenfrom the jets of pipes 60 passing through the spaces 3!, apparently causing oxidation of the surface of the steel strip passing from the tube I8, and

Preferably the valves in the found that if the proportions vary to increase the amount of air in the fuel, darker shades are obtained. It is thought that the carbon monoxide reduces the oxidizing eifect of the gas mixture below that of atmospheric oxygen to pre- 5 vent the color of the steel from being too dark or red. A uniform, smooth, beautiful blue oxide may thus be imparted to the strip by properly regulating the valves.

After passing through the furnace, the steel 10 strip is guided between a pair of chilling blocks a in the form of jackets through which water is circulated. The steel strip is thus hardened without losing its blue finish. Thereafter, the strip maypass between a pair of water cooled 15 chambers 8|. The members 8! are formed with central, longitudinal chambers 82 communicating with the center of the strip and receiving burners 83 for heating the midportion of the strip adjacent the slots 12. Inthis manner 20 the longitudinal mid-portion of the steel strip is annealed and softened to permit bending of the blades when placed in the razor. The steel strip may thereafter pass over an electrically heated tempering device 85 maintained preferably at 25 about 450 F. for imparting the proper temper thereto.

The steel strip thus has the color imparted to it before the hardening operation is entirely completed. The color is formed on the steel strip 30 independently of the tempering operation, and gives-no indication of the temper of the steel.

It will thus be seen that there is provided a method in which the several objects of this invention are achieved, and which is well adapted 5 to meet the conditions of practical use.

As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiment set forth, it is to be understood that all matter here- 40 in set forth or shown in the accompanying drawing, is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim as new and desire to secure by Letters atent: i-

1 The method of producing colored nd hardened strip steel, which consists in passing the strip through an elongated chamber and heating said strip to a temperature approximating 1400 F. by burning a mixture of airunder pressure and 50 carbon monoxide, permitting the products of combustion of the the mixture resulting from said burning to reach the strip by entering said elongated chamber only at a constricted point thereof, said point being adjacent the end at 55 which the strip passes out of the furnace, then chilling the strip to harden it with the surface oxidation thus produced, and then annealing the longitudinal midportion of said strip.

2. The method of producing colored and hara- 60 ened strip steel, which consists in passing the strip through'an elongated chamber and heating said strip to a temperature approximating 1400 F. by burning a mixture of air and carbon monoxide, permitting the products of combustion of 5 the mixture resulting from said burning to reach the strip by entering said elongated chamberonly at a constricted pointthereof, said point being adjacent the end atwhich the strip passes out of the furnace, then chilling the strip to harden 7 it with the surface oxidation thus produced, then annealing the longitudinal midportion of said strip, and then tempering the entire strip"inde- I pendently of the oxidized color imparted thereto.

3. A process of hardening and bluing sheet 75 steel consisting in heating. a chamber to a temperature above the critical point of the steel by burning jets of a gaseous mixture comprising air and carbon monoxide outside of said chamber,

passing said sheet steel through said chamber during the heating operation and maintaining the steel out of contact with the products of combustion from the jets until the sheet steel is about to exit from said chamber and permitting the products of combustion to contact the sheet steel adjacent the exit point.

4. A process of hardening and coloring steel consisting in passing the steel through a furnace, heating the steel as it passes through the furnace to a temperature above its critical point by burning a gaseous mixture comprising air and carbon monoxide, preventing the products of combustion resulting from said burning from reaching the steel as it passes through the combustion chamber of said furnace, and permitting the products of combustion to reach the steel only at a point in the furnace adjacent to where the strip emerges from the furnace.

5. A process of hardening and coloring steel consisting in passing the steel through a furnace, heating the steel as it passes through the furnace to a temperature above its critical point by burning a gaseous mixture comprising air and carbon monoxide, preventing theproducts of combustion resulting from said burning from reaching the steel as it passes through the combustion chamber of said furnace, and permitting the products of combustion to reach the steel only at a point in the furnace adjacent to where the strip emerges from the furnace, and thereafter chilling the steel.

6. A process of hardening and coloring steel consisting in'passing the steel through a furnace, heating the steel as it passes through the, furnace to a temperature above its critical point by burning a gaseous mixture comprising air and carbon monoxide, preventing the products of combustion resulting from said burning from reaching the steel as it passes through the combustion chamber of said furnace, and permitting the products of combustion to reach the steel only at a point in the furnace adjacent to where the strip emerges from the furnace, thereafter chilling the steel, and thereafter tempering the steel.

7. A process of hardening and coloring strip steel consisting in passing said strip through a chamber located in a furnace, burning oxygen adjacent the strip as the strip enters the furnace, heating said strip to a temperature above its critical point by burning in said furnace jets of a gaseous mixture comprising air and carbon monoxide, permitting only constricted commum cation between the chamber and the furnace whereby the products of combustion within the furnace are permitted to reach the strip.

.8. A process of hardening and coloring steel consisting in passing the steel through a furnace, playing a flame on the steel as the same enters the furnace, heating the steel as it passes through the furnace to a temperature above its critical point 'by burning in the combustion chamber of the furnace jets of a gaseous mixture comprising air and carbon monoxide and preventing the products of combustion within the chamber from reaching the steel as it passes through the combustion chamber except at a constricted point in the furnace adjacent to where the strip emerges from the furnace.

9. A process of hardening and coloring strip steel, consisting in passing said strip through a tube located in the combustion chamber of a furnace, playing a flame on the strip as the strip enters said tube, and heating said strip to a temperature above. its critical point by burning in the combustion chamber of said furnace jets of a gaseous mixture comprising air and carbon monoxide and allowing the products of combustion resulting from said burning to enter the chamber at a constricted point adjacent the end of the tube at which the .strip passes out of the furnace.

10. A process of producing a blue color on strip steel consisting in passing the strip through an elongated chamber, heating the strip within the chamber to a temperature above the critical point of the steel and passing into the chamber and to the strip after the same has been heated to a temperature above critical point, products of combustion resulting from the burning of jets of a gaseous mixture comprising air and carbon monoxide, with the air constituent of the mixture being supplied in excess of the amount burned in the jet. I

11. A process of producing a blue color on strip steel consisting in passing the strip through an elongated chamber, burning oil and other products from the surface of the strip as it enters said chamber, heating the strip within the chamber to a temperature above the critical point of the steel and passing into the chamber and to the strip after the same has been. heated to a temperature above critical point, products of combustion resulting from the burning of jets of a gaseous mixture comprising air and carbon monoxide, with the air constituent of the mixture being supplied in excess of the amount burned in the jet.

F. ARTHUR 'I'UERFF. 

